Tool for inserting wire coil screw threads



April 29, 1958 J. o. FORSTER 2,832,129

TOOL FOR INSERTING WIRE con SCREW THREADS Filed Jan. 11, 1954 i mmll 26INVENTOR. John O. Forster l6 BY M 7 ATTORNEY aesa ae of 28 and thebottom of the member in, a compression spring is inserted whichfurnishes the required force to clamp the coil end B between the layers28 and 21. When a torque in the direction of: the arrow A is applied tothe tube 5;"! both members and ll will be taken along owing to pin 22bearing ainst the slot fianlt 24.

In using the tool a certain downward pressure is generally to be appliedwhich however should not exceed a certain maximum in order to avoid adeformation of the coil end B beyond its limit of elasticity. For thisreason, a driving piece 31 is telescopically connected with the tube 27by means of two opposite pins 32 which are so cured in the side wall ofpiece and project into slots 3?, respectively of the tube 27. A secondspring 34 of slight force is interpositioned between an inner shoulder35 of the tube 2 and the bottom 31' of the head portion of the piece31.. Thus, unless the tool is handled contrary to directions, the onlyforcerernaining against the lower part of the tool is exerted by thesplin T he top end 39 of the driving piece 31 is so formed that a torquecan be applied to it. In. the illustrated embodiment, the top end 35? isstandard Morse cone for use with a power tool spindle. if another driveis to be used the top end may be shaped accordingly.

Means are provided for shifting the member limited distance upwards inrelation to member lit against the restraint of the spring Bill in orderto release a coil end B from clamping engagement, or to spread themembers 1t) and it apart for the reception of a coil cud E. These meanscomprise the aforementioned inclined slots 16 of member ill into whichthe pin 22 engages, and a collar 36 screwed on the thread 15' andsecured in a desired position by a set screw 37. Collar 36 serves as agrip to turn the member ill in the direction of the arrow A whereby themember ltl will be raised owing to the pin 22 hearing against theinclined side 26 of slot 2L6. Thereby the clamping faces at 29 and 21will be spread apart so that a coil end E be placed therebetween,whereupon by a turn of the collar 36 in the opposite d rection the clampwill be closed. It will be clear that for the purpose just described ascrew thread connection between the collar and member ltl would not berequired and that any other gripping means provided on or in connectionwith the member Iii) could be substituted. However in the illustratedembodiment the adjustable collar 36 serves a second purpose. in manyinstances, it is desired that a coil C will be inserted into the hole ofa boss B to a predetermined depth. This can be attained with the aid ofthe collar. When namely in the course of the inserting operation thelower face 38 of the collar comes to bear on another surface, as e. g.the top surface of the boss into which the coil has been screwed,further advancement of the member lid in the axial direction will bestopped. However, the rotation and simultaneous axial movement of memberill will continue as the pin 2.2 can move axially downward in slot .lti.Thereby the clamp constituted by members Zltl and 11 Will open so as torelease the coil end E and permit it to spring outward. Now, it will beclear that by turning the collar in relation to member lid in the one orthe other direction and, then, securing it by means of set screws 37,the depth to which a coil will be inserted by means of the tool can beadjusted.

Instead of the form illustrated in Fig. 2, L shaped slots 16, may beused as shown in Fig. 3. Each slot 16 has an axially directed arm 24-and a peripherally directed arm 25. During the operation of the tool thepin 22 will be movable in the axial arm For the purpose. however, ofopening the clamp, the slotted member in will be shifted upwards andthen turned so that the pin 22 can enter the ieripheral arm and hold theclamp open. To close the clamp member 1% will be turned back whercuponspring will urge member Elli downward while pin 22 moves up. arm 25.

It has been stated that in most instances the coils to be 1.. A. at usii. slot inserted with the aid of the tool are of a diameter larger thanthe corresponding diameter of the hole in the boss to be lined by thecoil which therefore has to be con tracted during or before theinsertion. This contraction is accomplished by a contracting torqueacting between the leading coil end and a portion of the coil body. inother words, if a torque is applied to the coil end in the direction thecoil is wound, a reaction must take hold of some portion of the coilbody to resist the turning in order to cause the required contraction.This reaction can be set up by the friction between the coilconvolutions and the wall or thread flanks of the hole in the boss.However, in most instances it is preferable to use a so-called prewindere. g. a device consisting of a plate or block P having a conical innerscrew thread of a maximum diameter according to a coil prior to beingcontracted and a minimum diameter according to the diameter to which thecoil is to be contracted. (A prewinder of such kind is more fullydescribed e. g. in U. 8. Patent No. 2,316,231 to Evans.) The prewinderdenoted by P is shown in Fig. l positioned on the top surface S of aboss B provided with a threaded hole H to be lined with too coil C. Theprewinder P may be held in correct position by hand or it may be securedby means not shown either to the boss B or to a stationary part of thetool.

In order to use the tool, it will be raised above the top surface of theprewinder or if no prewindcr is employed above the top surface of theboss so high that a coil E can he slid from below on the member it Thewire of which the coil is wound may be of any suitable and desiredcross-section. By gripping the collar which is fixed in a desiredposition, the bottom 12 of member 10 will be separated from head 17 ofmember 11 in the manner explained in the description of the slots in, or16. .Then the end convolution E will be pushed between the layers 20 and21 whereupon the member 10 will be turned back to clamp the convolutionE between the two members. The coil in this position will be slightlyspaced from the cylindrical member lit the diameter of which should beequal to or a little smaller than the inner diameter of the coil afterthe latter has been contracted. Thereupon the tool will be lowered intothe hole H of the boss with the head of member 11 leading. By applying atorque and slight downward pressure to the upper end of piece 31 thecoil will be screwed through the prewinder or directly into the hole Hof the boss B whereby the coil will be contracted to seat properly inthe hole H. When the desired depth is reached 1'. c. When the properlyadjusted collar 36 abuts against either the top surface of the prewinderor of boss B, the convolution E will be released and spring back to itsoriginal form or at least approximately to that form. The tool may thenbe withdrawn. In order to render the withdrawal possible even if theconvolution B does not spring back to the same diameter as the remainderof the coil, it is advisable to make the diameter of member 11 somewhatsmaller than that of member 1 After the withdrawal, the tool is ready tobe loaded with another coil.

It will be apparentto those skilled in the art that many alterations andmodifications of the structure shown and described are possible withoutdeparture from the essence and spirit of the invention which for thatreason shall not be limited but by the scope of the appended claims.

I claim:

1. A tool for inserting a screw thread forming wire coil as a lining ina hole of a boss, comprising in coaxial relationship a first hollowcylindrical member iusertable in a coil for which the tool is destined,and having its bottom end closed except for a central opening, said endhavinga substantially flat outer bottom surface, the diameter of saidbottom surface being slightly smaller than that of the body of saidfirst cylindrical member, a second member including a substantially flatcylindrical head facing said bottom surface and being of 'a diametersimilar to that of said bottom surface, and a shank extending throughsesame said central opening into said first member, a spring inside saidfirst member and operatively connected to said shank so as to urge saidhead towards said bottom surface of said first member, means connectedto one of said members to apply a torque thereto, one of said membersbeing provided with a slot, said other member including a pin transversewith respect to the axis of said member and engaging said slot, saidslot being substantially wider than said pin and extending partiallyaround the circumference of the slot-provided member at a slight angleto a plane transverse with respect to the axis of said member, saidfirst member further including an abutment adjustable in the axialdirection to engage a surface of said body when the tool is moved adesired distance in the direction towards said surface.

2. A tool for inserting a screw thread forming Wire coil as a lining ina hole of a boss, comprising in co-axial relationship a first hollowcylindrical member insertable in a coil for which the tool is destined,and having its bottom end closed except for a central opening, said endhaving a substantially flat outer bottom surface, the diameter of saidbottom surface being slightly smaller than that of the body of saidfirst cylindrical member, a second member including a substantially fiatcylindrical head facing said bottom surface and being of a diametersimilar to that of said bottom surface, and a shank extending throughsaid central opening into said first member, a spring inside said firstmember and operatively connected to said shank so as to urge said headtowards said bottom surface of said first member, means connected to oneof said members to apply a torque thereto, one of said members beingprovided with a slot, said other member including a pin transverse withrespect to the axis of said member and engaging said slot, said slotbeing substantially wider than said pin and extending partially aroundthe circumference of the slot-provided member at a. slight angle to aplane transverse with respect to the axis of said member, said firstmember being provided with an external screw thread, a collar screwed onsaid external thread, and a set screw in said collar to secure thelatter in an adjusted position for engagement with a surface of saidboss.

References Cited in the file of this patent UNITED STATES PATENTS2,108,252 Cooper Feb. 15, 1938 2,319,377 Wallace et al. May 18, 19432,344,750 Stoltz Mar. 21, 1944 2,364,288 Haggerty Dec. 5, 1944 2,586,805Forster Feb. 26, 1952 2,641,052 Fennema et al. June 9, 1953

